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20 amp plugs vs. 15 amp plugs

Hi,
I am switching some of my larger tools to 240. I had a professional electrician install 240 20 amp circuit so I should be safe there.
I went out and bought plugs to put on my tools and realized that I picked up 20 amp plugs. My tools all say I should use plugs rated at 15 amp. If I put the 20 amp plugs on the tools will I be safe?

I assume you're talking about tools that will operate at 240 volts and not your 120 volt tools. The plug for 240 volts is different from a 20 amp 120 volt plug and you should make sure you're using the 240 volt plug.

Beyond that, if you wire it up correctly there's no problem with using a higher amp rated plug.

Mike

Go into the world and do well. But more importantly, go into the world and do good.

With two separate 220 circuits in and around my shop, I had to standardize plugs so I could move some of the machines around. The circuits have a breaker capacity of 30 amps each. But I had more 20 amp machines than 30, amp, so now my six 220 machines all have the 20amp size plugs.

Often the reason the spec is for a 15amp plug and breaker is to protect the tool - wire/motor. Using a higher breaker (20amp) will not protect the electrical parts of the tool if something goes wrong. My grinder is very clear that it should be connected to a 15amp 240v circui.

The proper way to set this up is to plug the tool per spec and then match this to the outlet and to the correct breaker. It does make for more outlets.

I have a friend that got some 30amp plugs/outlets on the cheap and put his 240 volt tools on 30amp breakers. Wire was cheap years back and his runs were short -- but this is not a safe way to wire a shop.

I have a friend that got some 30amp plugs/outlets on the cheap and put his 240 volt tools on 30amp breakers. Wire was cheap years back and his runs were short -- but this is not a safe way to wire a shop.

Although it is considered "Overkill", It does not hurt anything to use a higher amp plug AND a corresponding larger wire on anything. It is the circuit breaker amp rating that controls the safety of the circuit, so in your friend's case, the circuit will be fine but he can replace the 30 amp Breakers with 20 amp breakers if he is trying to protect the tools with the circuit breaker, (even though that is NOT what the ckt Brkr is intended to protect). What IS truly unsafe is to use a smaller wire and lower amp plug than what is called for by the tool's specs, because the tool is then drawing more current than the wire and plug are designed to handle, which will cause the wire and plug to heat up and possibly catch fire. Additionally, the use of the lower amp circuit will eventually cause major damage to the tool's motor.

"Some Mistakes provide Too many Learning Opportunities to Make only Once".

I do not want to get into anything over this topic -- but this can be a very dangerous subject to overlook.

You do not want to place a higher amp plug and then by its very nature a higher amp circut onto any electrical device. The breaker is there to protect the entire circuit - not just the wire in the wall.

The overkill -- can kill.

If a tool has a 15 amp spec, the motor and other wires/ lineset are built around that spec, and to allow an overcurent is just not a good idea.

A motor built around a 15amp spec allowed 20amp with a locked rotor will tell you real fast it is not happy.

We are talking about TWO different items in a shop 240v circit.

The outlet must match the breaker rating with a wire gauged to at least match the rating of the breaker.

The tool rating is another matter - and you should not allow a tool to be installed in a circuit greater then its rated spec.

You do not want to place a higher amp plug and then by its very nature a higher amp circut onto any electrical device.

I completely agree with the second part, but not the first. There is no reason why you can't use a higher rated plug. Likewise, I can run 10/2 wire for a 15A circuit as well. I don't need to, 14/2 will do, but it doesn't make it any more or less safe. My shop has 20A and 15A circuits. I don't have to swap the plug on my sander when I move it from one outlet to another.

The breaker is an entirely different matter of course. Always use the breaker appropriate for the wiring and usage.

Also, your advice on not using too large a circuit is great. Just because it works or because it's code doesn't mean you can't make it safer.

In theory, you could wire your whole house with 30A circuits, but then what's the point of having breakers to begin with? The previous owners of my house did this. There was a loose connection in an outlet, which would cause the breaker (15A) to trip. So, they replaced it with a 30A breaker. No more tripping. No more protection either!

The original post was on the topic of replacing 15A plugs with 20A plugs so that they can then be installed on a properly wired 20A 240V circuit -- this is not correct - no way no how.

If the tool indicated that it should be on a max 15A 240V circuit it should have a 15A 240 plug connected to 15A 240V outlet and a 15A 240V breaker.

The ratings on all equipment are the requirements of that equipment. They are also the minimum ratings for any circuit or device they connect into. If your tool says 15 amps, then you can plug it into any receptacle on any circuit capable of supplying at least 15 amps. It does no harm to the tool at all to plug it in on a circuit our outlet with larger capacity than needed to run the tool as long as the voltage is correct. You can damage tools by placing them on circuits not capable of supplying enough volts and amps. You can safely plug a tool into a 100 amp circuit if the voltage is correct without damaging the tool. IF there is a problem internally in the tool, the circuit breaker is not likely going to come to your aid and prevent permanent damage to the tool. Motors are generally protected with overcurrent or over temperature devices internally.

Circuit breakers are designed to protect the wiring of the circuits they support not necessarily the devices plugged into them. Like wise receptacle ratings are designed to protect the receptacle from damage. You should not use a 15 amp receptacle or switch on a circuit that will be drawing more than 15 amps. The receptacles and switches should also match the circuit breaker rating since they are part of the wiring. Wiring size should never have less rating than the circuit breaker. You can use heavier wire if you want, but it is basically wasting money.

Lee Schierer - McKean, PA

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Am I missing something here? If you have a tool that states that it needs 15A MAX (I personally have not found this on any tools) and you have a 20A circuit with properaly sized wire, outlet, and breaker, then AS AN OPTION you could switch the breaker to a 15A breaker. Then your wire would be oversided, but the breaker would prevent the tool from receiving more than 15A.